Spectrometer for the spectral analysis of a specimen

Abstract

The present invention relates to a spectrometer for the spectral analysis of a specimen. The spectrometer comprises a radiation source (01) for irradiating the specimen with electromagnetic radiation and a dispersive element (02) for the spatiospectral splitting of the radiation reflected by the specimen. A measurement window (04) is used to transmit the radiation generated by the radiation source (01) to the specimen and to transmit the radiation reflected by the specimen to the dispersive element (02). The radiation generated by the radiation source (01) runs on a first inner beam path (06) from the radiation source (01) to the measurement window (04). The radiation reflected by the specimen runs on a second inner beam path (07) from the measurement window (04) to the dispersive element (02). A spatially resolving detector (03) is used for the wavelength-dependent conversion of the spatiospectrally split electromagnetic radiation. A deflecting mirror (14) located on the first inner beam path (06) and on the second inner beam path (07) is used to jointly deflect the first inner beam path (06) and the second inner beam path (07).

Description

[0001] Spectrometer for spectral analysis of a sample

[0002] The present invention relates to a spectrometer for the spectral analysis of a sample. The spectrometer comprises a measuring window for transmitting electromagnetic radiation from a radiation source to the sample and for transmitting the electromagnetic radiation reflected by the sample to a dispersive element for the spatial-spectral splitting of the electromagnetic radiation reflected by the sample. The spectrometer is designed, for example, for the analysis of the ingredients of agricultural products or foodstuffs, for which purpose it is arranged, for example, on a harvesting machine.

[0003] State-of-the-art spectrometers for inline and atline process measurement technology for agricultural and food applications are known. Moisture values ​​and ingredients can be measured directly using NIR spectroscopy and associated calibrations. Such spectrometers can be used stationary or mobile. Since NIR spectroscopy is an optical measurement method, the measurement accuracy depends essentially on the individual components of the spectrometer and the measurement setup that forms the interface to the sample. The measurement window can become dirty and scratched during use. If such a spectrometer is used on a forage harvester, for example, in extreme cases the protective flanges are worn away by the material flow and have to be replaced. This means that changes in measurement performance will occur over the entire service life.Aging phenomena, such as those caused by a halogen lamp, also affect the measurement. To keep these changes within a defined tolerance range, the spectrometer must be readjusted through cyclic recalibration. In the manufacture of such spectrometers, a set of gray standards is typically used to verify the linearity of the spectrometer. However, mirrors, white standards, wavelength standards, and black references can also be used for this purpose.

[0004] DE 10 2004 021 448 B4 shows a spectrometric reflection measuring head with internal recalibration. It consists of a housing with a window, in which an illumination source and an optical assembly for collecting and coupling the measuring light into a light guide are arranged. The housing has connections to a spectrometer. The housing also contains at least two standards for internal recalibration, which can be optionally pivoted into the beam path of the reflection measuring head for recalibration.

[0005] From DE 10 2004 048 103 B4 an arrangement for determining the components of harvested agricultural products is known. This arrangement comprises a spectrometric measuring head which consists of a housing provided with a window, in which there is an illumination source, a spectrometer arrangement and at least two standards for internal recalibration. The standards can be swivelled into the beam path of the measuring head so that the entire measuring light emanating from the illumination source is used for recalibration. DE 10 2018 103 509 B3 shows a method for sample-accurate measurement using a mobile ingredient analysis system which has a housing with a window, an interface for an external reference unit, a display and control unit, a light source, an optical spectrometer, a camera, an internal reference unit and an electronic control unit.

[0006] DE 10 2017 108 552 B4 relates to a spectrometric measuring head with a measuring surface that can be positioned opposite an examination surface of a sample. The measuring head comprises a light source and at least one illumination window in the measuring surface, through which light provided by the light source is emitted towards the examination surface of the sample. At least two transmitted light entrance windows are also positioned in the measuring surface and allow light remitted by the sample to enter. Each transmitted light entrance window is spaced from the illumination window by a predetermined, different amount.

[0007] DE 10 2007 007 040 A1 teaches a measuring device for the optical and spectroscopic examination of a sample. The measuring device comprises a housing, a first light source, a window, an optical spectrometer with a dispersive element, and a number of detector elements. An incident aperture of an electronic camera is directed through the window onto the sample. It is proposed that a second light source be associated with the camera.

[0008] US 2014 / 0362382 A1 shows a device for detecting matter. The device comprises a first light source for emitting a first light beam and a second light source for emitting a second light beam. The first light beam and the second light beam are directed onto a scanning element in the form of a rotatable polygonal mirror. The scanning element deflects the first light beam and the second light beam onto the matter to be detected. A detector receives light reflected from the matter via the scanning element. The detector can be a spectrometer.

[0009] DE 10 2009 050 371 B3 discloses a method for the spectrometric measurement of a material flow moving in a longitudinal direction. According to this method, an illumination region on the material flow is illuminated by an illumination beam generated by a radiation source. Radiation reflected from a measurement region on the material flow is at least partially collected by optical components and transmitted to a spectrometer. The illumination region covers the measurement region. The illumination region and the measurement region are stationary in the longitudinal direction. The radiation transmitted to the spectrometer is then subjected to spectrometric analysis.

[0010] EP 1 740 928 B1 shows a method for the internal recalibration of a spectrometric measuring head. An illumination source, a spectrometer arrangement and at least two internal standards for recalibration are arranged in a housing provided with a window. Measurement values ​​are acquired and processed by a processor and transmitted to a bus system via an interface. The internal standards are optionally swiveled into the beam path of the measuring head in such a way that the measurement light emanating from the illumination source is used for recalibration and measurement data of the internal standards are acquired by the spectrometer arrangement, so that recalibration can be carried out using the measurement data of the internal standards and stored measurement values ​​for at least two additional external standards.

[0011] DE 10 2017 217 280 A1 discloses a measuring device for particle measurement, comprising a measuring chamber and a transmitting device for generating an optical signal for feeding into the measuring chamber. A receiving device receives the optical signal from the measuring chamber via a first optical path to determine any influence of particles in the measuring chamber on the optical signal.

[0012] The object of the present invention, starting from the prior art, is to provide a spectrometer which is designed, for example, for the ingredient analysis of agricultural products on a harvesting machine and which has a low overall height in order to be able to be arranged on the harvesting machine in a space-saving manner. For example, on a harvesting machine it is often necessary to arrange the spectrometer above an ejector of the harvesting machine at the highest position of the harvesting machine, where the overall height of the spectrometer directly determines the overall height of the harvesting machine. For the harvesting machine to be road-legal, a maximum overall height must be observed, so there is a requirement to be able to design the spectrometer with a very low overall height.

[0013] The above object is achieved by a spectrometer according to the appended claim 1.

[0014] The spectrometer according to the invention is used to measure a

[0015] Spectrum of electromagnetic radiation in order to spectrally analyze a sample. The electromagnetic radiation is preferably ultraviolet radiation, visible light and / or infrared radiation. The spectrometer is in particular an optical measuring system for determining the ingredients of a sample on a spectroscopic basis. It is preferably used to determine the ingredients of agricultural products, harvested goods or foodstuffs. In this respect, the respective agricultural product or harvested goods or foodstuff forms the sample for the spectral analysis. The spectrometer is preferably arranged on an agricultural machine, such as a forage harvester or another agricultural machine, and is designed for the continuous testing of an agricultural product or harvested goods. The spectrometer is preferably designed for a reflection measurement.The spectrometer is preferably designed as a polychromator.

[0016] For continuous testing of the agricultural product, the crop either flows past the spectrometer or the spectrometer is moved past the crop. Based on calibrations, the measurement results can be used to determine various components such as moisture, protein, starch, oil content, and / or properties such as cutting length, fiber condition, or temperature of the crop.

[0017] The spectrometer comprises a radiation source for irradiating the sample with electromagnetic radiation. The electromagnetic radiation is preferably ultraviolet radiation, visible light and / or infrared radiation. In this respect, the radiation source is preferably formed by a light source. The electromagnetic radiation generated by the radiation source strikes the sample and is at least partially reflected by the sample. The reflected electromagnetic radiation is spectrally analyzed by the spectrometer in order to draw conclusions about the sample and its contents as well as other properties.

[0018] The spectrometer includes a dispersive element for spatially spectrally splitting the electromagnetic radiation reflected from the sample. The electromagnetic radiation is diffracted or refracted by the dispersive element to varying degrees depending on the wavelength, resulting in a spectrum of the reflected electromagnetic radiation.

[0019] The spectrometer comprises a measuring window for transmitting the electromagnetic radiation generated by the radiation source from the radiation source to the sample and for transmitting the electromagnetic radiation reflected by the sample from the sample to the dispersive element. A window axis of the measuring window is aligned perpendicular to the measuring window.

[0020] The electromagnetic radiation generated by the radiation source runs along a first inner beam path from the radiation source to the measuring window. The first inner beam path thus represents part of an illumination beam path. The electromagnetic radiation reflected by the sample runs along a second inner beam path from the measuring window to the dispersive element. The second inner beam path thus represents part of a measuring beam path. The spectrometer also includes a spatially resolving detector for the wavelength-dependent conversion of the spatially spectrally split electromagnetic radiation. Locations on the spatially resolving detector are each assigned to a wavelength of the spatially spectrally split electromagnetic radiation. The spatial resolution of the detector therefore enables a wavelength-dependent measurement to be carried out.

[0021] The spectrometer further comprises a deflection mirror arranged on the first inner beam path and on the second inner beam path for jointly deflecting the first inner beam path and the second inner beam path. Thus, on its path from the radiation source to the measuring window, the first inner beam path passes the deflection mirror, where the first inner beam path is deflected. On its path from the measuring window to the dispersive element, the second inner beam path passes the deflection mirror, where the second inner beam path is also deflected.The deflection of the two inner beam paths makes it possible for the radiation source and the dispersive element to be arranged horizontally next to the window axis rather than in the usually vertically aligned window axis, so that the overall height of the spectrometer can be reduced without having to miniaturize the components of the spectrometer, which is usually not possible due to robustness requirements with regard to vibrations, shocks and temperature range.

[0022] A particular advantage of the spectrometer according to the invention is that it can be designed as a compact reflection measuring head, for example, for a harvesting machine. Thus, the spectrometer can be arranged above a discharge manifold of the harvesting machine for chopped material without significantly increasing the overall height of the harvesting machine, which is limited to 4.00 m for road approval, or without losing height for functionally important components of the harvesting machine, such as balloon tires.

[0023] A further advantage of the spectrometer according to the invention is that the requirements previously placed on spectrometers for the ingredient analysis of agricultural products on harvesting machines can still be met despite the reduced overall height of, for example, 60 mm to 80 mm. For example, a measuring spot on the spectrometer can have a diameter of at least 20 mm, which is necessary, for example, for the analysis of corn due to the size of the corn kernels and the inhomogeneity of the sample. The integration time occurring during measurement with the spectrometer can be limited to a maximum of 15 ms, which corresponds, for example, to a measurement with five ingredient values ​​per second and a material speed of up to 100 km / h. An optical measuring geometry previously used in the state of the art can be retained in order to be able to continue using calibration models that have already been created.In this respect, the spectrometer can be designed to be downward compatible, so that the previously customary distance and angle to the sample remain unchanged and accessories for such spectrometers, such as a flange, a turntable and sample dishes can still be used. Preferably, an angle between the illumination beam path and a normal on a plane of the sample or the window axis of the measuring window is therefore selected as was selected when creating calibration models with spectrometers according to the state of the art. In preferred embodiments, the deflection mirror is designed to deflect the first inner beam path and the second inner beam path by a deflection angle which is between 60° and 120°. The deflection angle is more preferably between 80° and 100°. The deflection angle is particularly preferably 90° taking manufacturing tolerances into account.This enables a particularly compact design of the spectrometer.

[0024] A first section of the first inner beam path is formed between the radiation source and the deflecting mirror. A first section of the second inner beam path is formed between the deflecting mirror and the dispersive element. The first section of the first inner beam path and the first section of the second inner beam path are preferably arranged together in a first plane. The naming of the first sections used here serves merely to distinguish them and is not related to the temporal formation of the respective beam path.

[0025] A second section of the first inner beam path is formed between the deflecting mirror and the measuring window. A second section of the second inner beam path is formed between the measuring window and the deflecting mirror. The second section of the first inner beam path and the second section of the second inner beam path preferably lie together in a second plane. The window axis preferably also lies in the second plane. The second plane is preferably arranged perpendicular to the first plane. The naming of the second sections used here merely serves to distinguish them and is not related to the temporal formation of the respective beam path. In preferred embodiments, the first plane is arranged horizontally. The second plane is preferably arranged vertically. In this case, the deflection angle is 90°.

[0026] The measuring window is preferably located in a horizontal plane. The measuring window is preferably arranged above or below the deflection mirror, depending on the position in which the spectrometer is used. The measuring window is particularly preferably arranged below the deflection mirror, depending on the position in which the spectrometer is aligned for the examination of a sample located below the spectrometer.

[0027] A third inner beam path is preferably formed from the dispersive element to the spatially resolving detector. The third inner beam path thus forms part of the measuring beam path. The third inner beam path is preferably also arranged in the first plane, so that the three inner beam paths lie together in the first plane, at least in sections.

[0028] In a first preferred embodiment, the deflecting mirror is fixedly arranged within the spectrometer. The spectrometer preferably further comprises a movable reference carrier with at least one optical reference which can be pivoted into the first inner beam path and into the second inner beam path between the deflecting mirror and the measuring window. The optical reference can in particular be pivoted into the second section of the first inner beam path and into the second section of the second inner beam path. The optical reference is preferably formed by a white standard, a gray standard or a black standard. The reference carrier preferably comprises at least two of the optical references, which preferably comprise a white standard and a black standard.

[0029] The reference carrier is preferably formed by a rotatable turntable. The reference carrier is rotatable about an axis of rotation which is preferably arranged parallel to the second plane. The axis of rotation is preferably arranged parallel to the window axis. The rotatable turntable is preferably divided into several circular sectors, one of the circular sectors being radiation-permeable in order to enable measurements of the sample with the spectrometer. One or more of the circular sectors each have one of the at least one optical reference. To calibrate the spectrometer, one of the optical references must be pivoted into the first inner beam path and into the second inner beam path between the deflection mirror and the measuring window by rotating the rotatable turntable. This makes the respective optical reference effective, so that a reference measurement can be carried out with the spectrometer using the optical reference.

[0030] In a second preferred embodiment, the deflecting mirror can be tilted between a first tilted position and a second tilted position and back. The first tilted position represents the position required for measuring the sample, in which position, as described above, the deflecting mirror is aligned to form and jointly deflect the first inner beam path and the second inner beam path. In the second tilted position, the deflecting mirror is aligned to reflect the electromagnetic radiation generated by the radiation source onto the dispersive element. The electromagnetic radiation therefore does not reach the measuring window and therefore also not the sample, but is directed directly to the dispersive element, enabling an internal reference measurement, namely an internal white measurement, by means of which the spectrometer can be calibrated.In the second tilted position, the deflecting mirror can be inclined by an angular difference of, for example, 10° from a direct connecting line to the dispersive element. The deflecting mirror can be designed for angle-dependent reflection, so that not all of the incoming radiation from the radiation source is reflected to the dispersive element, but rather is partially transmitted by the deflecting mirror and / or partially absorbed by the deflecting mirror. Alternatively or additionally, the deflecting mirror can have an electrochromic layer. The electrochromic layer is preferably made of a material that changes the light transmission depending on an applied DC voltage.Consequently, the transmission and thus also the reflection of the deflection mirror are electrically controllable, so that the reflection can be reduced, particularly in the second tilt position, whereby not all of the incoming radiation from the radiation source is reflected to the dispersive element.

[0031] The deflecting mirror can preferably be tilted about a tilt axis between the first tilt position and the second tilt position. The tilt axis thus represents an axis of rotation. The tilt axis preferably lies in the first plane, so that the tilt axis is preferably arranged horizontally. The tilt axis preferably lies in the deflecting mirror. The tilt axis preferably lies in a central axis of the deflecting mirror. The spectrometer preferably comprises a tilt actuator for tilting the deflecting mirror between the first tilt position and the second tilt position and vice versa.

[0032] In a third preferred embodiment, the deflecting mirror can be pivoted between a first pivoting position and a second pivoting position, and vice versa. The first pivoting position represents the position required for measuring the sample, in which position, as described above, the deflecting mirror is aligned to form and jointly deflect the first inner beam path and the second inner beam path. In the first pivoting position, the deflecting mirror is also arranged between a reference carrier of the spectrometer, which carries at least one optical reference, on the one hand, and the radiation source and the dispersive element, on the other. Consequently, no relevant radiation from the radiation source reaches the reference carrier because the deflecting mirror is located in between. Likewise, no radiation reaches the reference carrier from the radiation source to the dispersive element because the deflecting mirror is located in between.The reference carrier carries at least one optical reference. The reference carrier can be fixedly arranged within the spectrometer; in particular if the reference carrier comprises exactly one optical reference; for example if the optical reference also has an electrochromic layer, which enables different reference measurements. The reference carrier can also comprise a plurality of the optical references and be designed to be displaceable and / or rotatable in order to direct one of the optical references towards the radiation source. The optical references preferably comprise a white standard, a grey standard and / or a black standard. In the second pivoting position, the deflecting mirror releases a beam path from the radiation source to the reference carrier and also a beam path from the reference carrier to the dispersive element.This causes the radiation from the radiation source to travel from the radiation source to the reference carrier, where it is reflected and / or absorbed by the optical reference and / or transmitted by the optical reference, with the reflected portion of the radiation reaching the dispersive element. Thus, the electromagnetic radiation does not reach the measurement window and therefore also not the sample; instead, the portion of the electromagnetic radiation reflected by the optical reference is directed directly to the dispersive element, enabling an internal reference measurement based on the optical reference, which can be used to calibrate the spectrometer.In the second pivoting position, the deflecting mirror is arranged pivoted out of an imaginary connecting line between the reference carrier with the at least one optical reference and the radiation source and out of an imaginary connecting line between the reference carrier with the at least one optical reference and the dispersive element.

[0033] The deflecting mirror is preferably pivotable about a pivot axis between the first pivot position and the second pivot position. The pivot axis thus represents an axis of rotation. The pivot axis is preferably parallel to the first plane, so that the pivot axis is preferably arranged horizontally. The pivot axis is preferably offset from the first plane. The pivot axis is preferably arranged at a distance from a plane encompassing the deflecting mirror.

[0034] The spectrometer preferably comprises a swivel actuator for

[0035] Swiveling the deflection mirror between the first swivel position and the second swivel position and vice versa.

[0036] The third preferred embodiment preferably additionally comprises the movable reference carrier described in connection with the first preferred embodiment between the deflection mirror and the measuring window, which is preferably formed by a rotatable turntable.

[0037] In a fourth preferred embodiment, the deflection mirror is fixedly arranged within the spectrometer and has an electrochromic layer so that the reflection of the deflection mirror is electrically controllable and can be reduced, in particular, for a reference measurement.

[0038] The spectrometer is preferably designed such that a first optical path length from the radiation source via the deflection mirror to the sample and back from the sample via the deflection mirror to the dispersive element, and a second optical path length from the radiation source to the optical reference and back from the optical reference to the dispersive element, are of equal length. It is advantageous that the pivotable deflection mirror allows these two optical path lengths to be kept of equal length, so that the calibrations can be carried out particularly accurately using the at least one reference.

[0039] In preferred embodiments, the deflecting mirror is inclined by 45° relative to the first plane. If the deflecting mirror is tiltable or pivotable, this inclination of preferably 45° applies to the first tilt position or the first pivot position. In preferred embodiments, the first section of the first inner beam path and the first section of the second inner beam path are at an angle to one another of between 10° and 60°. This angle is more preferably between 20° and 50°.

[0040] The first section of the first inner beam path has an angle of incidence at which it hits the deflecting mirror. The first section of the second inner beam path has an angle of reflection at which it leaves the deflecting mirror. The angle of incidence and the angle of reflection are preferably equal.

[0041] In preferred embodiments, the spectrometer comprises a housing in which the radiation source, the dispersive element, the spatially resolving detector, and the deflection mirror are arranged. The measuring window forms part of an upper side or a lower side of the housing. The measuring window preferably forms part of the lower side of the housing. The housing has a height which is preferably at most 80 mm, more preferably at most 60 mm, and even more preferably at most 40 mm. A particular advantage of the spectrometer is that it can be designed as a compact reflection measuring head with a low overall height, for example for a harvesting machine. The spectrometer can thus be arranged above a discharge spout of the harvesting machine for chopped material, without the overall height of the harvesting machine, which is limited to 4.00 m, for example, for road approval of the harvesting machine, being significantly increased orHeight is lost for functionally important components of the harvester, such as balloon tires. The spectrometer also preferably includes at least one external optical reference located outside the housing.

[0042] The dispersive element is preferably formed by a diffraction grating. Thus, the electromagnetic radiation to be analyzed, which is reflected by the sample, is diffracted at the diffraction grating. The electromagnetic radiation to be analyzed, which is diffracted by the diffraction grating, is directed onto the spatially resolving detector. The dispersive element can alternatively be formed by another element that diffracts the light. The dispersive element can alternatively be formed by a light-refracting element, such as a prism.

[0043] The spatially resolving detector is preferably formed by a detector array. The detector array comprises at least linearly arranged detector elements, which can also be referred to as pixels.

[0044] The spectrometer preferably further comprises a control and measurement signal processing unit in the form of a computing unit. The control and measurement signal processing unit serves to control the radiation source and to process an output signal of the spatially resolving detector and, if applicable, to control the tilt or swivel actuator and / or the electrochromic layer. The control and measurement signal processing unit preferably comprises a graphical user interface for operating the spectrometer. The control and measurement signal processing unit preferably has data interfaces, which can also be wireless. The control and measurement signal processing unit is preferably configured so that the spectrometer calibrates itself.

[0045] In preferred embodiments, the spectrometer further comprises a beam splitter and an electronic image converter. The beam splitter is arranged on the second inner beam path and splits a partial camera beam path from the second inner beam path. The partial camera beam path is directed directly or indirectly at the image converter. Thus, the second inner beam path serves not only to spectrally analyze the sample with the aid of the dispersive element and the spatially resolving detector, but also to image the sample with the image converter. To this extent, the spectrometer comprises an integrated camera based on the electronic image converter. An image of the sample imaged by the image converter can be displayed so that an operator of the spectrometer can visually capture the sample in order to detect, for example, impurities in the sample.Alternatively or additionally, the image of the sample can be processed mechanically, for which purpose the control and measurement signal processing unit is preferably configured. A particular advantage of the camera integrated into the spectrometer based on the electronic image converter is that by splitting the second inner beam path, the image converter can be integrated into the spectrometer in a space-saving manner without the overall height of the spectrometer having to be increased. For this purpose, the camera partial beam path is preferably located in the first plane, in which the first section of the first inner beam path between the radiation source and the deflection mirror and the first section of the second inner beam path between the deflection mirror and the dispersive element also lie.Another particular advantage is that the integrated camera is directed at the area of ​​the sample being spectrally examined by the spectrometer, since the image for the image converter is also coupled out of the second inner beam path. This ensures that those interfering influences, such as reflections, that actually impair the spectral examination can be visually identified in the camera image. The beam splitter and the image converter are preferably also arranged in the spectrometer housing.

[0046] The beam splitter is preferably formed by a partially transparent mirror. The partially transparent mirror is preferably arranged at an inclination of 45° to the second inner beam path, so that the camera partial beam path has an angle of 90° to the second inner beam path. Alternatively, the beam splitter can also be formed by a beam splitter prism or the like. The beam splitter is preferably designed for the spectral splitting of the second inner beam path, wherein the camera partial beam path preferably comprises only the visual part of the electromagnetic spectrum.

[0047] In preferred embodiments, the beam splitter is arranged on the second inner beam path between the deflection mirror and the dispersive element, so that it is located in the first section of the second inner beam path.

[0048] The electronic image converter is preferably a CMOS image converter or a CCD image converter. The electronic image converter can also be referred to as an image sensor or camera chip. The electronic image converter is preferably designed to convert color images. The electronic image converter is preferably designed to convert moving images.

[0049] In preferred embodiments, the spectrometer comprises a camera lens arranged on the camera beam path between the beam splitter and the image converter. The camera lens images the sample onto the image converter. The camera lens is preferably also located in the housing. The camera lens and the image converter form the integrated camera.

[0050] In preferred embodiments, the image converter forming an image plane, the camera lens forming an objective plane, the beam splitter, the deflecting mirror and an object plane of the sample arranged parallel to the measuring window are arranged relative to one another in such a way that the Scheimpflug condition is met. According to the Scheimpflug condition, the focal plane, objective plane and image plane intersect in a common straight line. The focal plane should lie in the object plane formed by the sample. During measurement, the sample is located outside the spectrometer in front of the measuring window, with the object plane formed by the sample being arranged parallel to the measuring window. A measuring distance is formed between the object plane and the measuring window.The Scheimpflug condition must be observed because, due to the inclined viewing direction of the second inner beam path, the object plane is not perpendicular to the axis of the second inner beam path. This requires an image plane that is also inclined to the axis in order to image the object plane completely sharply. However, by observing the Scheimpflug condition, the image is imaged completely sharply. In this case, the Scheimpflug condition must be applied, taking into account the deflection at the deflection mirror and the deflection at the beam splitter.

[0051] Compliance with the Scheimpf lug condition results in the image converter being inclined relative to the camera beam path.

[0052] Further details and developments of the invention will become apparent from the following description of preferred

[0053] Embodiments of the invention, with reference to the drawing. Shown are:

[0054] Fig. 1: a schematic diagram of a first preferred embodiment of a spectrometer according to the invention during a sample measurement;

[0055] Fig. 2: the first preferred embodiment shown in Fig. 1

[0056] Embodiment of the spectrometer during sample measurement in another view;

[0057] Fig. 3: the first preferred embodiment of the spectrometer shown in Fig. 1 during a reference measurement;

[0058] Fig. 4: the first preferred embodiment shown in Fig. 3

[0059] Embodiment of the spectrometer during the reference measurement in another view;

[0060] Fig. 5: a schematic diagram of a second preferred embodiment of the spectrometer according to the invention during a reference measurement;

[0061] Fig. 6: the second preferred embodiment shown in Fig. 5

[0062] Embodiment of the spectrometer during the reference measurement in a further view; Fig. 7: a schematic representation of a third preferred embodiment of the spectrometer according to the invention during a sample measurement;

[0063] Fig. 8: the third preferred embodiment of the spectrometer shown in Fig. 7 during sample measurement in a further view;

[0064] Fig. 9: the third preferred embodiment of the spectrometer shown in Fig. 7 during a reference measurement;

[0065] Fig. 10: the third preferred embodiment shown in Fig. 9 during the reference measurement in a further view;

[0066] Fig. 11: a schematic diagram of a fourth preferred embodiment of the spectrometer according to the invention during a sample measurement;

[0067] Fig. 12: the fourth preferred embodiment of the spectrometer shown in Fig. 11 during a reference measurement;

[0068] Fig. 13: a schematic diagram of a fifth preferred embodiment of the spectrometer according to the invention during a sample measurement;

[0069] Fig. 14: the fifth preferred embodiment of the spectrometer shown in Fig. 13 during a reference measurement; Fig. 15: a schematic diagram of a sixth preferred

[0070] Embodiment of the spectrometer according to the invention; and

[0071] Fig. 16: the sixth preferred embodiment shown in Fig. 15

[0072] Design form in another view.

[0073] Fig. 1 shows a schematic diagram of a first preferred embodiment of a spectrometer according to the invention during a spectral measurement of a sample 40 (shown in Fig. 15). Arranged in a housing (not shown) of the spectrometer are a light source 01, a diffraction grating 02, and a detector array 03, which serve for the spectral analysis of the sample 40 (shown in Fig. 15). The housing (not shown) has a measurement window 04, which is to be directed onto the sample 40 (shown in Fig. 15).

[0074] The light generated by the light source 01 (not shown) travels along a first inner beam path 06 from the light source 01 to the measuring window 04, from which it exits and strikes the sample 40 (shown in Fig. 15). The sample 40 (shown in Fig. 15) reflects this light (not shown) according to its reflective properties. The reflected light (not shown) passes through the measuring window 04 into the spectrometer and travels along a second inner beam path 07 from the measuring window 04 to the diffraction grating 02. On this second inner beam path 07, the light passes through a first lens 08, through a slit 09, through a shutter 11 and through a second lens 12. After passing through the diffraction grating 02, the light passes through a third lens 13 before striking the detector row 03.The spectrometer further comprises a deflecting mirror 14, which serves to jointly deflect the first inner beam path 06 and the second inner beam path 07. In the preferred embodiment shown, a deflection of 90° occurs. The deflecting mirror 14 is fixed in the first preferred embodiment shown, so that a tilting axis 16 is not used here.

[0075] The spectrometer further comprises a reference carrier 17 in the form of a rotatable turntable. The reference carrier 17 carries optical references 18. For measuring the sample 40 (shown in Fig. 15), the reference carrier 17 is rotated such that none of the references 18 are located in the first inner beam path 06 and the second inner beam path 07.

[0076] A sapphire crystal 21 is arranged above the measuring window 04 to protect the measuring window 04. A diaphragm 22 is located below the measuring window 04.

[0077] A first section 23 of the first inner beam path 06 between the light source 01 and the deflection mirror 14 as well as a first section 24 of the second inner beam path 07 between the deflection mirror 14 and the diffraction grating 02 lie together in a first plane (not shown), which is aligned horizontally. A second section 26 of the first inner beam path 06 between the deflection mirror 14 and the measuring window 04 as well as a second section 27 of the second inner beam path 07 between the measuring window 04 and the deflection mirror 14 lie together in a second

[0078] Level (not shown) which is arranged perpendicular to the first level (not shown) so that it is aligned vertically.

[0079] Fig. 2 shows the first preferred embodiment shown in Fig. 1

[0080] Embodiment of the spectrometer in a further view. In this further view, the second section 26 of the first inner beam path 06 and the second section 27 of the second inner beam path 07 can be seen.

[0081] Fig. 3 shows the first preferred embodiment of the spectrometer shown in Fig. 1 during a reference measurement. For the reference measurement, the reference carrier 17 was rotated so that one of the references 18 (shown in Fig. 4) is located in the first inner beam path 06 and in the second inner beam path 07.

[0082] Fig. 4 shows the first preferred embodiment of the spectrometer shown in Fig. 3 during the reference measurement in a further view. In this further view, the reference 18 can be seen in particular.

[0083] Fig. 5 shows a schematic diagram of a second preferred embodiment of the spectrometer according to the invention during a reference measurement. This second preferred embodiment is initially similar to the first preferred embodiment shown in Fig. 1. In contrast to the first preferred embodiment shown in Fig. 1, the second preferred embodiment has a fixedly arranged reference carrier 29 with a reference 30 instead of the rotatable reference carrier 17. In contrast to the first preferred embodiment shown in Fig. 1, in the second embodiment the deflecting mirror 14 can be pivoted or tilted about a pivot axis 31 between a first pivot position and a second pivot position.In the second pivoting position shown here, the deflecting mirror 14 releases a beam path 32 from the light source 01 to the reference 30 located on the fixed reference carrier 29 and a beam path 33 from the reference 30 located on the fixed reference carrier 29 to the diffraction grating 02.

[0084] Fig. 6 shows the second preferred embodiment of the spectrometer shown in Fig. 5 during the reference measurement in a further view. In this further view, the position of the deflection mirror 14 during the reference measurement can be seen in particular.

[0085] Fig. 7 shows a schematic diagram of a third preferred embodiment of the spectrometer according to the invention during the measurement of a sample 40 (shown in Fig. 15). This third preferred embodiment is initially similar to the second preferred embodiment shown in Fig. 5. In contrast to the second preferred embodiment shown in Fig. 5, the pivot axis 31 of the deflecting mirror 14 in the third preferred embodiment is arranged outside a plane comprising the deflecting mirror 14. In the illustration shown, the deflecting mirror 14 is in its first pivot position, in which it is aligned to form the first inner beam path 06 and the second inner beam path 07. The deflecting mirror 14 is arranged in its first pivot position between the reference 30 located on the reference carrier 29 on the one hand and the light source 01 and the diffraction grating 02 on the other. Fig.Figure 8 shows the third preferred embodiment shown in Figure 7.

[0086] Embodiment during the measurement of the sample 40 (shown in Fig. 15) in a further view. In this further view, the position of the deflection mirror 14 during the measurement of the sample 40 (shown in Fig. 15) can be seen in particular.

[0087] Fig. 9 shows the third preferred embodiment shown in Fig. 7 during a reference measurement. For this purpose, the deflecting mirror 14 is in its second pivot position, in which it releases the beam path 32 from the light source 01 to the reference 30 located on the fixed reference carrier 29 and the beam path 33 from the reference 30 located on the fixed reference carrier 29 to the diffraction grating 02.

[0088] Fig. 10 shows the third preferred embodiment shown in Fig. 9 during the reference measurement in a further view. In this further view, the beam path 32 from the light source 01 to the reference 30 located on the fixed reference carrier 29 can be seen in particular.

[0089] Fig. 11 shows a schematic diagram of a fourth preferred embodiment of the spectrometer according to the invention in a cross-sectional view during the measurement of a sample 40 (shown in Fig. 15). This fourth preferred embodiment is initially similar to the first preferred embodiment shown in Fig. 1. In contrast to the first preferred embodiment shown in Fig. 1, this fourth preferred embodiment also has the fixedly arranged reference carrier 29 with the reference 30 shown in Fig. 5. As in the second preferred embodiment shown in Fig. 5, the deflecting mirror 14 can be pivoted or folded about the pivot axis 31 between the first pivot position and the second pivot position, but in the fourth preferred embodiment shown here the pivot axis 31 is arranged significantly outside a plane comprising the deflecting mirror 14.In the illustration shown, the deflecting mirror 14 is in its first pivoted position, in which it is aligned to form the first inner beam path 06 and the second inner beam path 07. In its first pivoted position, the deflecting mirror 14 is arranged between the reference 30 located on the reference carrier 29, on the one hand, and the light source 01 and the diffraction grating 02, on the other. In this cross-sectional view, it can be clearly seen that the first section 23 of the first inner beam path 06 between the light source 01 and the deflecting mirror 14 and the first section 24 of the second inner beam path 07 between the deflecting mirror 14 and the diffraction grating 02 lie together in the first plane (not shown).In the same way, it can be seen that the second section 26 of the first inner beam path 06 between the deflecting mirror 14 and the measuring window 04 and the second section 27 of the second inner beam path 07 between the measuring window 04 and the deflecting mirror 14 lie together in the second plane (not shown), which is arranged perpendicular to the first plane (not shown).

[0090] Fig. 12 shows the fourth preferred embodiment of the spectrometer shown in Fig. 11 during a reference measurement. For this purpose, the deflecting mirror 14 is in its second pivoted position, in which it releases the beam path 32 from the light source 01 to the reference 30 located on the fixed reference carrier 29 and the beam path 33 from the reference 30 located on the fixed reference carrier 29 to the diffraction grating 02. Since in the fourth preferred embodiment shown here the pivot axis 31 is arranged significantly outside the plane comprising the deflecting mirror 14, the deflecting mirror 14 is located in its second pivoted position far outside the released beam paths 32, 33.

[0091] Fig. 13 shows a schematic diagram of a fifth preferred embodiment of the spectrometer according to the invention in a cross-sectional view during the measurement of a sample 40 (shown in Fig. 15). This fifth preferred embodiment is initially similar to the fourth preferred embodiment shown in Fig. 11. In contrast to the fourth preferred embodiment shown in Fig. 11

[0092] This fifth preferred embodiment does not have the rotatable reference carrier 17. A further difference lies in the position of the pivot axis 31, which in the fifth preferred embodiment shown here is arranged significantly outside the plane encompassing the deflection mirror 14 near the reference 30. The deflection mirror 14 is in the illustration shown in its first pivot position, in which it is aligned to form the first inner beam path 06 and the second inner beam path 07. The deflection mirror 14 is in its first pivot position between the plane shown on the

[0093] Reference carrier 29 on the one hand and the light source O1 and the diffraction grating O2 on the other hand. Fig. 14 shows the fifth preferred embodiment of the spectrometer shown in Fig. 13 during a reference measurement. For this purpose, the deflecting mirror 14 is in its second pivoted position, in which it releases the beam path 32 from the light source O1 to the reference 30 located on the fixed reference carrier 29 and the beam path 33 from the reference 30 located on the fixed reference carrier 29 to the diffraction grating O2. Since in the fifth preferred embodiment shown here the pivot axis 31 is arranged significantly outside the plane comprising the deflecting mirror 14, the deflecting mirror 14 is located in its second pivoted position far outside the released beam paths 32, 33.

[0094] Fig. 15 shows a schematic diagram of a sixth preferred embodiment of the spectrometer according to the invention. This sixth preferred embodiment is initially similar to the first preferred embodiment shown in Fig. 1. In contrast to the first preferred embodiment shown in Fig. 1, the sixth preferred embodiment does not have a reference carrier with references. The sixth preferred embodiment shown has an integrated camera formed by a camera lens 41 and an image converter 42. The camera lens 41 comprises a plurality of lenses 43 and an aperture 44.So that an image can be recorded by the integrated camera formed by the camera lens 41 and the image converter 42, a partially transparent mirror 46 is located in the first section 24 of the second inner beam path 07, which mirror separates a partial camera beam path 47 from the second inner beam path 07, which is directed via the camera lens 41 onto the image converter 42. The image converter 42 is inclined relative to the partial camera beam path 47 in order to maintain the visual immunization condition.

[0095] In addition, sample 40 located above the measuring window 04 is shown.

[0096] Fig. 16 shows the sixth preferred embodiment shown in Fig. 15 in a further view. This illustration particularly shows how the camera partial beam path 47 is decoupled from the second inner beam path 07.

[0097] List of reference symbols

[0098] 01 Light source

[0099] 02 Diffraction grating

[0100] 03 Detector line

[0101] 04 Measuring window

[0102] 05

[0103] 06 first inner beam path

[0104] 07 second inner beam path

[0105] 08 first lens

[0106] 09 Gap

[0107] 10

[0108] 11 Closure

[0109] 12 second lens

[0110] 13 third lens

[0111] 14 deflecting mirrors

[0112] 15

[0113] 16 tilting axis

[0114] 17 reference carriers

[0115] 18 optical reference

[0116] 19

[0117] 20

[0118] 21 Sapphire crystal

[0119] 22 aperture

[0120] 23 first section of the first inner beam path

[0121] 24 first section of the second inner beam path

[0122] 25

[0123] 26 second section of the first inner beam path

[0124] 27 second section of the second inner beam path

[0125] 28

[0126] 29 fixed reference carrier 30 optical reference

[0127] 31 Swivel axis

[0128] 32 Beam path

[0129] 33 Beam path

[0130] 34

[0131] 35

[0132] 36

[0133] 37

[0134] 38

[0135] 39

[0136] 40 samples

[0137] 41 Camera lens

[0138] 42 image converters

[0139] 43 lenses

[0140] 44 aperture

[0141] 45

[0142] 46 partially transparent mirror

[0143] 47 Camera beam path

Claims

Patent claims 1. A spectrometer for the spectral analysis of a sample (40), comprising: a radiation source (01) for irradiating the sample (40) with electromagnetic radiation; a dispersive element (02) for the spatial-spectral splitting of the electromagnetic radiation reflected by the sample (40); a measuring window (04) for transmitting the electromagnetic radiation generated by the radiation source (01) to the sample (40) and for transmitting the electromagnetic radiation reflected by the sample (40) to the dispersive element (02), wherein the electromagnetic radiation generated by the radiation source (01) travels along a first inner beam path (06) from the radiation source (01) to the measuring window (04), and wherein the electromagnetic radiation reflected by the sample (40) travels along a second inner beam path (07) from the measuring window (04) to the dispersive element (02);a spatially resolving detector (03) for wavelength-dependent conversion of the spatially and spectrally split electromagnetic radiation; and a deflecting mirror (14) arranged on the first inner beam path (06) and on the second inner beam path (07) for jointly deflecting the first inner beam path (06) and the second inner beam path (07); 2. Spectrometer according to claim 1, characterized in that the deflection mirror (14) is designed to deflect the first inner beam path (06) and the second inner Beam path (07) to deflect a deflection angle of 90°.

3. Spectrometer according to claim 1 or 2, characterized in that a first section (23) of the first inner beam path (06) between the radiation source (01) and the deflecting mirror (14) and a first section (24) of the second inner beam path (07) between the deflecting mirror (14) and the dispersive element (02) are arranged together in a first plane.

4. Spectrometer according to claim 3, characterized in that a second section (26) of the first inner beam path (06) between the deflecting mirror (14) and the measuring window (04) and a second section (27) of the second inner beam path (07) between the measuring window (04) and the deflecting mirror (14) are arranged together in a second plane which is arranged perpendicular to the first plane.

5. Spectrometer according to one of claims 1 to 4, characterized in that the deflecting mirror (14) is tiltable between a first tilting position and a second tilting position, wherein the deflecting mirror (14) is aligned in the first tilting position for the joint deflection of the first inner beam path (06) and the second inner beam path (07), and wherein the deflecting mirror (14) is aligned in the second tilting position for a reflection of the electromagnetic radiation generated by the radiation source (01) onto the dispersive element (02).

6. Spectrometer according to one of claims 1 to 4, characterized in that the deflecting mirror (14) is fixedly arranged within the spectrometer, wherein the spectrometer further comprises a movable reference carrier (17) with at least one optical reference (18) which can be pivoted into the first inner beam path (06) and into the second inner beam path (07) between the deflecting mirror (14) and the measuring window (04).

7. Spectrometer according to one of claims 1 to 4, characterized in that the deflecting mirror (14) is pivotable between a first pivoting position and a second pivoting position, wherein the deflecting mirror (14) is aligned in the first pivoting position to form the first inner beam path (06) and the second inner beam path (07) and is arranged between a reference carrier (29) with at least one optical reference (30) on the one hand and the radiation source (01) and the dispersive element (02) on the other hand, and wherein the deflecting mirror (14) in the second pivoting position releases a beam path (32) from the radiation source (01) to the reference carrier (29) and a beam path (33) from the reference carrier (29) to the dispersive element (02).

8. Spectrometer according to claim 7, characterized in that a first optical path length from the radiation source (01) via the deflection mirror (14) to the sample (40) and back from the sample (40) via the deflection mirror (14) to the dispersive element (02) and a second optical path length from the radiation source (01) to the optical reference (18; 30) and back from the optical reference (18; 30) to the dispersive element (02) are of equal length.

9. Spectrometer according to one of claims 1 to 8, characterized in that the deflecting mirror (14) or the optical reference (18; 30) has an electrochromic layer.

10. Spectrometer according to one of claims 1 to 9, characterized in that it comprises a housing in which the radiation source (01), the dispersive element (02), the spatially resolving detector (03) and the deflection mirror (14) are arranged, wherein the measuring window (04) forms part of an upper side or a lower side of the housing, and wherein the housing has a height which is at most 80 mm.

11. Spectrometer according to one of claims 1 to 10, characterized in that it comprises a beam splitter (46) and an image converter (42), wherein the beam splitter (46) is arranged on the second inner beam path (07) and splits a camera partial beam path (47) from the second inner beam path (07), which partial camera beam path is directed towards the image converter (42).

12. Spectrometer according to claim 11, which refers back to claim 10, characterized in that the beam splitter (46) and the image converter (42) are arranged in the housing.

13. Spectrometer according to claim 11 or 12, characterized in that the beam splitter (46) is arranged on the second inner beam path (07) between the deflection mirror (14) and the dispersive element (02).

14. Spectrometer according to one of claims 11 to 13, characterized in that it comprises a camera lens (41), which is arranged on the camera beam path (47) between the beam splitter (46) and the image converter (42).

15. Spectrometer according to claim 14, characterized in that the image converter (42) forming an image plane, the camera lens (41) forming an objective plane, the Beam splitter (46), the deflection mirror (14) and an object plane parallel to the measuring window (04) are arranged relative to one another in such a way that the Scheimpf lug condition is met.

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